Inventor: Skill Increases

At 3rd level and every 2 levels thereafter, you gain a skill increase. You can use this increase to either become trained in one skill you're untrained in, or become an expert in one skill in which you're already trained.

At 7th level, you can use skill increases to become a master in a skill in which you're already an expert, and at 15th level, you can use them to become legendary in a skill in which you're already a master.